Electronic paper (sometimes also called electric paper and e-paper) has begun to replace legacy paper as an information source. It has many of the attributes of paper. For example it is writable, reflective and stable. Electronic paper can also be configured as a flexible and thin sheet, like paper.
Electronic paper can be used as an information source to be written to by multiple entities. In some circumstances a reader of electronic paper will want to reliably understand that a specific entity has written a particular type of information, and/or that a particular region of the electronic paper has been written to by a particular entity, or has been written subject to the occurrence of a specific event.